- Replace the rubber seal. Some of these have become brittle and deformed raising the possibility of leaks. Clark Rubber sell a circular cross-section foam seal that is a good replacement. This is glued in place with a shoe rubber sole adhesive.
- Hinges and handles will be lubricated with silicone grease.
- The frames will be cleaned with isocol.
- The windows will be polished. Car-body cutting compound or Brasso on a drill-mounted polishing cloth may do the trick. The intention is to restore the transparency of the windows which seems to be badly effected by very fine surface abrasions. These can also be cleaned with isocol and a polish (car wax?) applied. A little experimentation wouldn't go amiss.
- Check for leaks.
Here's a good old before / after shot. The product we finally went with - after a bit of experimenting - was Renovo Plastic Polish (available here).